BSG Guidelines for Post-polypectomy and Post-cancer-resection Surveillance

This document synthesizes the 2020 consensus guidelines from the British Society of Gastroenterology (BSG), the Association of Coloproctology of Great Britain and Ireland (ACPGBI), and Public Health England (PHE) for colorectal surveillance. These guidelines provide an evidence-based framework for surveillance colonoscopy in adults following the removal of premalignant polyps or resection of colorectal cancer (CRC). For the first time, these guidelines integrate national bowel cancer screening, incorporate surveillance for serrated polyps alongside adenomatous polyps, and aim to standardize follow-up for a broad cohort of patients.

The central recommendation is a simplified, unified risk stratification system. Patients are classified as “high-risk” for future CRC if they meet specific criteria based on the number and type of premalignant polyps found during an index colonoscopy.

Key Recommendations:

• High-Risk Criteria: A patient is considered high-risk if they have either:
  • Two or more premalignant polyps, including at least one advanced colorectal polyp.
  • Five or more premalignant polyps of any size.
• Surveillance Interval: High-risk patients should undergo a single surveillance colonoscopy at a 3-year interval. Patients not meeting high-risk criteria do not require colonoscopic surveillance and should be encouraged to participate in the national bowel screening programme.
• Post-CRC Resection: Patients should have a clearance colonoscopy within one year of their diagnosis, followed by a surveillance colonoscopy after three more years. Subsequent surveillance is determined by the post-polypectomy high-risk criteria.
• Stopping Surveillance: Surveillance is generally not recommended for individuals over the age of 75 or those with a life expectancy of less than 10 years, as the risks of the procedure may outweigh the benefits.
• Quality Emphasis: The guidelines strongly emphasize the critical importance of a high-quality index colonoscopy, including complete caecal intubation, adequate bowel preparation, and meticulous polypectomy technique, as this is considered more impactful in preventing CRC than subsequent surveillance.

Implementation of these guidelines is projected to significantly reduce the overall colonoscopic surveillance workload to approximately 20% of current levels, freeing up vital endoscopy resources for screening and symptomatic patients where pathology yields are higher.

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1. Guideline Overview and Aims

1.1. Introduction

Commissioned jointly by the BSG, ACPGBI, and PHE, these 2020 guidelines update the previous recommendations from 2010. They are the first to be developed since the introduction of national bowel cancer screening in the UK and provide a unified framework for surveillance after the resection of adenomatous polyps, serrated polyps, and colorectal cancer.

The primary objective is to provide an evidence-based framework for healthcare professionals to address three core questions:

1. Which patients should commence surveillance post-polypectomy and post-cancer resection?
2. What is the appropriate surveillance interval?
3. When can surveillance be stopped?

1.2. Core Surveillance Principles

The Guideline Development Group (GDG) established a set of core principles by consensus to underpin the recommendations:

• Primary Aim: To reduce Colorectal Cancer (CRC) incidence by identifying and resecting de novo and missed premalignant polyps after initial clearance has been achieved.
• Secondary Aim: To reduce CRC mortality by preventing cancer and detecting it at an earlier, more treatable stage.
• Risk-Based Approach: Surveillance should only be offered to individuals who remain at a higher risk of developing CRC compared to the general population, even after the risk reduction from the index polypectomy.
• Minimum Frequency: Surveillance should be performed at the minimum frequency required to achieve its aims. It should be discontinued when there is no evidence that it is required.
• Emphasis on Quality: Risk stratification for surveillance is predicated on a high-quality index colonoscopy, defined as a complete examination to the caecum with adequate bowel preparation and clearance of all identified premalignant polyps. A higher quality index procedure is considered more important for CRC prevention than subsequent surveillance.
• Balancing Risks and Benefits: The benefits of surveillance must be balanced against the risks of harm (e.g., colonoscopy complications, psychological distress) and costs to the patient and health service.
• Shared Decision-Making: Patients should be informed about the evidence, benefits, and risks of surveillance to facilitate shared decision-making.

2. Key Definitions

The guidelines use a standardized set of definitions for classifying polyps, which is crucial for applying the risk stratification criteria.

Term	Definition
Serrated Polyp	An umbrella term for hyperplastic polyps, sessile serrated lesions (SSLs), SSLs with dysplasia (SSLd), traditional serrated adenomas (TSA), and mixed polyps.
Premalignant Polyp	Includes both serrated polyps (excluding diminutive 1-5 mm rectal hyperplastic polyps) and adenomatous polyps.
Advanced Serrated Polyp	A serrated polyp ≥10 mm in size or containing any grade of dysplasia.
Advanced Adenomatous Polyp	An adenoma ≥10 mm in size or containing high-grade dysplasia. (Note: Tubulovillous or villous histology is not part of the UK definition).
Advanced Colorectal Polyp	An umbrella term that includes both advanced serrated polyps and advanced adenomatous polyps.
LNPCP	Large non-pedunculated colorectal polyp (≥20mm).

3. Core Surveillance Recommendations

The recommendations are synthesized into a single algorithm designed to simplify and standardize surveillance across different patient cohorts.

3.1. Post-Polypectomy Surveillance Algorithm

The central decision point is whether a patient meets the “high-risk” criteria following a baseline colonoscopy.

High-Risk Criteria

A patient is categorized as high-risk for future CRC if the index colonoscopy reveals:

• ≥2 premalignant polyps, including at least one advanced colorectal polyp; OR
• ≥5 premalignant polyps of any size.

Recommendation:

• Patients meeting the high-risk criteria should undergo a one-off surveillance colonoscopy 3 years later.
  • Strength of Recommendation: Strong
  • GRADE of Evidence: Low

Low-Risk Criteria

A patient is categorized as low-risk if they have had one or more premalignant polyps resected but do not meet the high-risk criteria.

Recommendation:

• Low-risk patients should not undergo colonoscopic surveillance. They should be strongly encouraged to participate in the national bowel screening programme when invited.
  • Strength of Recommendation: Strong
  • GRADE of Evidence: Low

Exceptions for Younger, Low-Risk Patients

• For low-risk patients who are more than 10 years younger than the lower age limit of the national screening programme (e.g., <40-50 years old), a surveillance colonoscopy may be considered after 5 or 10 years, individualized based on age and other risk factors.
  • Strength of Recommendation: Weak
  • GRADE of Evidence: Low

3.2. Post-Colorectal Cancer (CRC) Resection Surveillance

Recommendations:

1. Patients who have undergone a potentially curative CRC resection should have a clearance colonoscopy within one year of diagnosis.
   • Strength of Recommendation: Strong
   • GRADE of Evidence: Low
2. Following the clearance colonoscopy, the next surveillance should be performed after an interval of 3 years.
   • Strength of Recommendation: Strong
   • GRADE of Evidence: Low
3. The need for any further surveillance beyond this point is determined by the standard post-polypectomy high-risk criteria.

3.3. Surveillance for Large Non-Pedunculated Colorectal Polyps (LNPCPs)

The surveillance strategy for LNPCPs (≥20mm) depends on the method of resection.

Recommendations:

• En Bloc (R0) Resection: If an LNPCP is removed in one piece with clear margins (en bloc R0 resection), no site check is required. The patient should follow the standard post-polypectomy high-risk pathway and have a surveillance colonoscopy after 3 years.
  • Strength of Recommendation: Strong
  • GRADE of Evidence: Low
• Piecemeal Resection: If an LNPCP is removed in multiple pieces, more intensive site surveillance is required.
  1. A site check is performed 2-6 months after the initial resection.
  2. A further site check is performed at 18 months from the original resection to detect late recurrence.
  3. Once recurrence is excluded, the patient enters the standard high-risk pathway with a surveillance colonoscopy after 3 years.
  • Strength of Recommendation: Strong
  • GRADE of Evidence: Low

3.4. Ongoing and Cessation of Surveillance

Recommendations:

• The need for ongoing surveillance is re-evaluated at each procedure. If a patient meets the high-risk criteria at their 3-year surveillance colonoscopy, a further surveillance colonoscopy is recommended in another 3 years.
  • Strength of Recommendation: Strong
  • GRADE of Evidence: Low
• If a patient has no high-risk findings on a surveillance colonoscopy, they should cease colonoscopic surveillance and participate in the national bowel screening programme.
  • Strength of Recommendation: Strong
  • GRADE of Evidence: Low
• In general, surveillance should not be performed on patients older than 75 years or where comorbidity indicates a life expectancy of less than 10 years.
  • Strength of Recommendation: Weak
  • GRADE of Evidence: Low

3.5. Procedural and Pathological Considerations

• Polyp Size: Polyp size should be recorded as the largest dimension of neoplastic tissue as measured at histopathological examination. Endoscopic assessment should be used for piecemeal resections.
  • Strength of Recommendation: Strong
  • GRADE of Evidence: Moderate
• Colonoscopist Quality: Surveillance colonoscopies should only be performed by colonoscopists who are screening accredited or whose key performance indicators (KPIs) exceed the minimum standard.
  • Strength of Recommendation: Strong
  • GRADE of Evidence: Low

4. Alternative Surveillance Modalities

The guidelines evaluated non-colonoscopic surveillance methods, with the following recommendations:

• CT Colonography (CTC):
  • Post-Polypectomy: CTC is an acceptable alternative if colonoscopy is incomplete or not possible due to the patient’s clinical condition. The radiation risk is considered to be outweighed by the potential benefits. (Strength: Strong, Evidence: Very Low/High for radiation risk).
  • Post-CRC Resection: CTC should only be used if colonoscopy is contraindicated or not possible, due to evidence of poor performance in detecting polyps in the post-surgical colon. (Strength: Strong, Evidence: Moderate).
• Faecal Immunochemical Testing (FIT):
  • Not recommended for surveillance after resection of premalignant polyps due to insufficient evidence. Studies show it could miss 30-40% of CRCs and 40-70% of advanced adenomas in this setting. (Strength: Strong, Evidence: Low).
• Colon Capsule Endoscopy:
  • Not recommended for surveillance due to insufficient evidence and high rates of incomplete assessments in the limited available studies. (Strength: Strong, Evidence: Very Low).

5. Summary of Supporting Evidence

The GDG conducted systematic reviews to create evidence statements that informed the recommendations. Key findings include:

Factor at Index Colonoscopy	Association with Risk at First Surveillance (Advanced Adenoma, Advanced Neoplasia, or CRC)	Grade of Evidence
High-Grade Dysplasia	Some, but inconsistent, evidence of increased risk.	Moderate
Tubulovillous/Villous Histology	Consistent evidence of increased risk. (Note: Not included in UK high-risk criteria due to poor inter-observer agreement among pathologists).	Moderate
Polyp Size ≥20 mm	Consistent evidence of increased risk.	Moderate
Polyp Size ≥10 mm	Some, but inconsistent, evidence of increased risk.	Moderate
Multiplicity of Adenomas	Consistent evidence of increased risk of advanced adenomas and advanced neoplasia; inconsistent for CRC.	Moderate
Advanced Serrated Polyps	Evidence suggests they are risk-equivalent to advanced adenomas for future CRC risk.	Low
Inadequate Bowel Preparation	Consistent evidence of increased risk.	Low
Incomplete Index Colonoscopy	Consistent evidence of increased risk.	Low
Family History of CRC	Consistent evidence of no associated increased risk (in patients not meeting criteria for hereditary surveillance).	Moderate
Younger Age	Consistent evidence of decreased risk.	Moderate

6. Implementation and Future Directions

6.1. Workload Implications

Preliminary analysis suggests these guidelines will significantly reduce the demand for surveillance colonoscopy.

• The number of people entering post-polypectomy surveillance is estimated to fall to 25-33% of previous levels.
• Only an estimated 10% of those undergoing an initial surveillance procedure will qualify for a second.
• The overall colonoscopic surveillance workload is projected to decrease to approximately 20% of the present level. This will free up endoscopy capacity for higher-yield procedures like screening and symptomatic investigations.

6.2. Key Research Questions

The GDG identified several key areas for future research:

• Studies using long-term CRC incidence/mortality as primary endpoints.
• More robust evidence on the effectiveness of surveillance for patients with serrated polyps.
• Development of a personalized surveillance prognostic algorithm.
• Further evidence on when to safely stop surveillance.
• Evaluation of non-invasive technologies like FIT or other biomarkers for surveillance.
• Greater data on patient experience and preferences surrounding surveillance.